Observatories and telescopes:Herschel's 'Forty Foot' reflector, Slough- A giant telescope with a 1.2m mirror built in 1788.Birr Castle, Co. Offaly, (Ireland) - Built in 1845, the Earl of Rosse's 1.8m reflecting telescope, was used to discover the spiral from galaxies. This telescope was the world's largest until the opening of Mount Wilson and it was recently restored and opened to the public.Hale telescope, California (USA) - The Hale's 5m telescope was first used in 1949.Jodrell Bank, Cheshire- Britain's initial and once the world's largest radio telescope, with a 76m dish, began in operation in 1957.Hubble Space Telescope (HST) - It orbits 600km above Earth's atmosphere and was launched in 1990. HST can photograph far objects with 10 times the detail possible with ground based telescopes.Keck I & II Telescopes, Hawaii (USA) - Opened in 1992-96. Both are situated 4,000m up a Hawaiian mountain, above 40 percent of the Earth's atmosphere. These are the most powerful ground based instruments with a 10.82m total aperture which are made up of 36 hexagonal mirrors. Hobby-Eberly Telescope, Texas (USA) - This telescope is meant to gather light for spectrum analysis instead of visual exploration. Operational since 1999, its overall diameter of 11m making it one of the largest optical telescope ever made.Yerkes Observatory, Wisconsin (USA) - It was completed in 1897. This 1m telescope is the biggest refracting instrument made up to this time.Mount Wilson Observatory, California (USA) - Until the Hale, it was the world's largest. Installed in 1917 with a mirror size of 2.5mRoyal Observatory, London (UK) - It was founded in 1675 by King Charles II, but atmospheric and light pollution in London reduced its ability. In 1884, the Prime or Greenwich Meridian 0 degree, that passes through observatory was adopted because the basis for all measurement and mapping. Longitude measurements refer to eat or west of the meridian.Arecibo Observatory, Puerto Rico - This is the world's most powerful radio telescope completed in 1963. It is used for searching for quasars and the search for alien life forms under the SETI (Search for Extra Terrestrial Intelligence) programme. This telescope's large 305m dish features in James Bond movie Golden Eye (1995).First telescope:The first telescopes were made in 1608 by Dutch optician Hans Lippershey. Italian astronomer Galileo built his own soon after and used it to discover Jupiter's moons. The earliest form of telescope known as refracting telescope, produced a slight distortion of images (called aberration). Since about 1670, astronomers have preferred to use reflacting telescopes, which use mirrors that commit for the distortion.